The present invention relates to the field of disc drive data storage devices. More specifically, the invention relates to providing an electrical path between a head assembly and a gimbal assembly in a magnetic disc drive.
Disc drive data storage devices of the "Winchester" type are well known in the industry. Such devices utilize rigid discs coated with a magnetizable medium for storage of digital information in a plurality of circular concentric tracks. This information is written to and read from the discs using a transducing head carried on a head assembly mounted on an actuator mechanism which moves the head from track to track across the surface of the disc under control of electronic circuitry. The discs are mounted for rotation on a spindle motor which causes the discs to spin and the surface of the discs to pass under the head.
In such a disc drive, the head assembly "flies" over the surface of the disc as the disc rotates at high speed. The head assembly includes a transducing head which is carried on a slider which has aerodynamic properties allowing the head assembly to fly. The head assembly is mounted on a gimbal assembly which is carried on a load beam armature coupled to the actuator mechanism. The gimbal assembly allows the head assembly to tilt, thereby achieving aerodynamic equilibrium. The armature is spring loaded and counteracts a lifting force from the slider as the head assembly flies across the disc surface. The spring loaded armature and the aerodynamic lifting force reach an equilibrium based upon the aerodynamic properties of the slider and the speed of rotation of the disc.
It is important to provide an electrical ground to the head assembly through the armature to the chassis of the disc drive. This helps reduce the buildup of static electricity on the head assembly which can arc to the storage disc. Further, the electrical grounding of the head assembly helps reduce noise during readback of magnetically encoded information.
Typical prior art techniques of achieving an electrical connection between the head assembly and the gimbal assembly have included the use of a conductive adhesive. However, the conductive adhesive suffers from a number of drawbacks including increased labor and material costs as well as relatively high resistivity.
In the prior art, adhering the head assembly to the gimbal assembly required a number of manual steps. First, a non-conducting adhesive was applied to the gimbal assembly. This adhesive was typically non-conducting so as not to electrically short electrical contact pads carried on the head assembly. After the head assembly was bonded to the gimbal assembly, a second electrically conductive adhesive was manually applied. The second adhesive was applied around the edge of the interface between the head assembly and the gimbal assembly. This technique does not lend itself to automated assembly lines.
In typical prior art disc drives, the average resistivity of head gimbal assemblies, as measured between the head assembly and the gimbal assembly in which the head assembly is attached to the gimbal assembly through a conductive adhesive, was approximately 400 .OMEGA. with some ranging above 1000 .OMEGA..